Which method of drug testing is the best?

Detection periods

The following chart from LabCorp gives approximate detection periods for each substance by test type.^[1] The ranges depend on amount and frequency of use, metabolic rate, body mass, age, overall health, and urine pH. For ease of use, the detection times of metabolites have been incorporated into each parent drug. For example, heroin and cocaine can only be detected for a few hours after use, but their metabolites can be detected for several days in urine. In this type of situation, we will report the (longer) detection times of the metabolites.

• NOTE 1: Oral fluid or saliva testing results for the most part mimic that of blood. The only exception is THC. Oral fluid will likely detect THC from ingestion up to a maximum period of 18-24 hours
• NOTE 2: Urine can not detect current drug use. It takes approximately 6–8 hours or more post-consumption for drug to be metabolized and excreted in urine. Similarly, hair requires two weeks, and sweat, seven days.

Approximate values for detection periods

Substance	Urine	Hair	Blood
Alcohol	3–5 days via ethyl gluconoride (EtG) metabolite or 10–12 hours via traditional method	lifetime of hair	12 hours
Amphetamines (except meth)	1 to 2 days	up to 90 days	12 hours
Methamphetamine	2 to 4 days	up to 90 days	24 hours
Barbiturates (except phenobarbital)	2 to 3 days	up to 90 days	1 to 2 days
Phenobarbital	7 to 14 days	up to 90 days	4 to 7 days
Benzodiazepines	Therapeutic use: 3 days. Chronic use (over one year): 4 to 6 weeks	up to 90 days	6 to 48 hours
Cannabis	Light use: 2-7 days Prolonged use: 1-3 months	up to 90 days	12 days
Cocaine	3 to 300 days with exceptions for certain kidney disorders	up to 90 days	24 hours
Codeine	1 day	up to 30 days	12 hours
Cotinine (a break-down product of nicotine)	2 to 4 days	up to 90 days	2 to 4 days
Morphine	2 days	up to 90 days	6 hours
Heroin	2 days (single use) 2-5 (chronic)	up to 90 days	6 hours
LSD	2 to 24 hours	up to 3 days	0 to 3 hours
Methadone	3 days	up to 30 days	24 hours
PCP	14 days; up to 30 days in chronic users	up to 90 days	24 hours

This helpful information was provided by wikipedia.

Obviously the drugs remain longer in the hair follicle than they do any where else. American Toxicology recommends that both hair and urine drug testing be used for optimal results.

Urine Drug Testing

This procedure requires that one provide a sample of urine. Either a test card is used on site for immediate results (see "General" section), or the sample is sent away to a lab to undergo gas chromatography/mass spectrometry (also known as GCMS), high performance liquid chromatography or immunoassay analysis. The majority of tests administered in pre-hire and even most probate scenarios are of the immediate, and less accurate "at home" variety. Most "dip stick" type tests have higher thresholds for a positive than do the GCMS tests. If a positive result (drug presence indicated) is found, the sample is usually sent to a lab for GCMS confirmation. This is largely due to the costliness of GCMS labaratory testing and time it takes to process and receive results. The results of any urine test reflect factors including, but not limited to age, weight, race, and often these factors are what determines whether the test is valid or not.

The efficacy of urine testing is debatable due to systematic cheating. It is widely reported that sample substitution and adulteration occur frequently, and both are effective methods of avoiding would-be positive tests. There are a number of adulterant "masking" agents that are sold, though they are often nothing more than a simple diuretic and are rarely more effective than caffeine. Some people drink copious amounts of water to successfully dilute the concentration of drug metabolites in their urine below detectable thresholds. Often this results in clear samples that may be rejected on the grounds of being too dilute, although a complex B vitamin will make urine yellow despite this practice of waterloading. Specific gravity testing can be done to identify whether or not the sample is of dilute nature, though this is used infrequently on otherwise inconspicuous samples. The substance Niacin is also frequently used for its reported "flushing" effect, though this is also of disputable adeptness. Some types of urinalysis can detect the use of these "detox" products, though they are rarely used unless some facet of the sample is suspicious. Also, the wide availability of at home drug screens allows an individual to take their own test before they receive one, thus knowing the results ahead of time- giving the user further opportunity to dilute the sample or to find a substitute.

This helpful information was provided to us by Wikipedia.

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